Hi @ss ,
I suppose there is no need to check SIP-NAT is validity while using the VoIP.
If you want to disable NAT in SIP content, you can also set the protocol type in SIP service TCP to "none". This should also disable the SPI.
In most cases, you will need to sign in to your router with the admin password. Look under its security settings, uncheck SIP ALG, save and reboot your router. More advanced corporate firewalls may require further adjustment, such as port forwarding.
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